Process for preparing blasting gelatin



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Patented June 3, 1947 amsn PROCESS FOR PREPARING BLASTING GELATIN Henry W. Botts, Carthage, Mo., assignor to Hercules Powder Company, Wilmington, Del., a

corporation of Delaware Application June 29, 1943, Serial No. 492,680

This invention relates to an improved blasting gelatin and more particularly to a process of manufacturing a blasting gelatin of maximum density.

Blasting gelatin comprising nitroglycerin which has been gelled by the addition of nitrocellulose is one of the most powerful explosives known. It is ordinarily prepared by heating the nitroglycerin from about 100 to about 136 F. and stirring in the nitrocellulose until a rubbery gel is formed. This procedure requires 10 to 15 minutes. The product which is obtained is very diiicult to pack because of its rubbery nature. During the mixing operation, a considerable volume of air is trapped in the gelatin in the form of ne air bubbles which reduces density. The density of freshly prepared product is of the order of 1.35 g./'cc. which may be contrasted to the density of 1.6 g./cc. when no air is present.

The usual compositions f the blasting gelatin manufactured in the art, having a formulation of 91 to 93% of nitroglycerin, 6 to 8% of nitrocellulose, and about 1% of an acid acceptor or antacid such as chalk, have a density as manufactured of about 1.34 to 137 g./cc. The density of the gelatin increases gradually upon storage with decreasing sensitivity of the explosive to initiation by blasting caps. When the density exceeds about 1.5 g./cc the blasting gelatin may even fail to detonate when primed with a commercial No. 6 or No. 8 blasting cap.

Y The presence of nely-divided air bubbles in the blasting gelatin seems essential to make it sensitive to caps. When this loss of air is sufficient so that the density of the gelatin is greater than about 1.5 g./cc. it tends to become insensitive to the usual commercial caps.

In order to maintain the blasting gelatin at a relatively low density, that is, 1.3 to 1.4 g./cc., it has been the practice to modify the above formula by incorporating a few percent of carbonaceous ingredients of low density such as cork, balsa and bagasse. Thus the air is present in the form of the air cells in the carbonaceous ingredient and Unfortunately, the result of lowering density and the associated decrease in detonation velocity result in an appreciable lowering of the brisance of the blasting gelatin as compared to one in the density range 1.5 to 1.6 g./cc. For some purposes it is important to secure the maximum brisance, and sensitiveness to the ordinary commercial caps becomes less important, and, in fact, is undesirable. For example, in military uses a blasting gelatin of density of 1.5 g./cc. or higher is desirable in order to attain a high density of loading, maximum brisance and insensitiveness to rifle re. In these cases where the maximum brisance is desired it is important to have a blasting gelatin approaching themaximum density of 1.6 g./cc.

8 Claims. (Cl. 52-22) For blasting gelatins of this type an extra strength cap or a suitable booster is used to insure detonation at the maximum velocity.

In contradistinction to the prior art methods of preparing blasting gelatin, the present invention is directed to a process of initially preparing a blasting gelatin of maximum density, which is much easier to load into cartridges than prior art gelatin, has a greater brisance than prior art gelatin, and in addition possesses insensitiveness t0 rifle fire which makes it suitable for military uses.

Now, in accordance with this invention there is provided a process for preparing maximum density blasting gelatin which comprises cooling an explosive comprising nitroglycerin to a temperature below about 10 C., adding a mixture comprising nitrocellulose and an antacid to said explosive, mixing the mass thus formed with a minimum amount of agitation while maintaining said temperature, and discharging the cooled mixed mass and allowing said mass to warm and thereby gelatinize.

More specifically, it has been found in accordance with the present invention that if the nitrocellulose is stirred into a blasting gelatin comprising nitroglycerin under conditions such that gelation is retarded, the introduction of air bubbles can be largely eliminated, giving a gelatin ofmaximum density and brisance. By retarding the gelation of the nitroglycerin, the mixture may be kept fluid and poured into shells or other containers, gelation being allowed to take place after loading. The mixing conditions, especially temperature and time of mixing, require careful control so that gelation will not occur during the mixing and loading operation, yet will not be too long delayed afterward.

Having now indicated in a general Way the nature and purpose of the invention, there follows a more detailed description of preferred embodiments thereof with reference to the accompanying drawing in which: The figure is acomposte flow chart and diagrammatic representation of the apparatus employed, wherein the jacketed mixer I has a line 2 for conveying a coolant into the jacket of said mixer and a line 3 for conveying the coolant therefrom. The mixer may be, for example, a Talley mixer such as described in U. S. Patent 946,475, or any other suitable mixing device, provided with a iiuid impervious jacket. The coolant may be, for exampile, circulating cold water, brine, or any other suitable refrigerant. With reference to the iigure, it will be seen that the invention comprises placing an explosive comprising nitroglycerin into a jacketed mixer where it is cooled down, by suitable means, to a temperature from about -10 to about +10 C., depending on the particular formulation of the explosive. Nitrocellulose is added to the explosive together with 1% antacid and mixed until evenly dispersed throughout the explosive. A minimum of mixing should be used to prevent introduction of air bubbles. The

mixture is then poured into wax paper cartridges 4 parts by weight of nitrocellulose is added to the nitroglycerin together with about 1 part by Weight of chalk and the mass thus formed is mixed,

y thereby evenly dispersing the nitrocellulose and antacid throughout the nitroglycerin. The mixing is carried out with a minimum amount of agitation to prevent introduction of air bubbles.

This is accomplished by rotating the mixing spirals of the Talley mixer slowly for about 1 to 3 minutes. The contents of the mixer is then poured into commercial cartridges, for example, 2 x 8 inch, 4 x 16 inch, or others. 'I'he filled commercial cartridges are then allowed to warm up Table I [Percent by Weight] A B C D E F G Nitroglycerin 91 50 48 90 Diglycerin-tetranitrate. 4l 39 Nitroglycol Nitrocellulose 8 8 8 7 Camphor 4 Manioc meal ,z DNT Mononitro naphthalen i Chalk 1 l l l 100 100 100 l 100 100 100 Density, g./cc l. 55 to 1. 6 1. 5 t0 1.56 1.52t0 l. 56 l. 51 t0 l. 55 l. 5l to l. 55 l. 52 t0 1. 55 1.52 t0 l. 55

A composition such as .A and E should be cooled down to between 0 to 5 C. and should be poured within 10 to 15 minutes. For compositions such as B and C the temperature may be as high as +10 C. For a composition such as D the temperature would preferably be below 0 C. in the range 0 to -10 C. If the temperature is too low, the mixture becomes rather viscous and does not pour well. For composition A there is some danger of the mixture freezing as the temperature is below the freezing point of nitroglycerin, which is 13 C. However, owing to the phenomenon of supercooling this does not occur in the time required for mixing and pouring. It is preferable, however, that some othei1 ingredient be present as in the other formulas to lower the freezing point.

The densities shown vary somewhat according to the formulation as the other ingredients, nitroglycol, DNT, diglycerin tetranitrate, etc., lower the density. If these blasting gelatins were made r by the usual method of mixing, the densities would fall in the range of 1.3 to 1.4 g./cc. and would be sensitive to a No. 6 blasting cap and to riiie re when packed in tin cans. In contradistinction, the dense blasting gelatins made in acccrdance with the invention will in general be insensitive to commercial blasting caps and to rie iire.

-By way of example the following comparison is made:

Table II Formula' A Detonation Velocity jeieveljs Density 1.35 g./cc 7200 12m/see.1 Shoots. Density 1.59 g./cc 7800 m./sec.2 Fails.

to room temperature, whereby the nitrocellulose dissolves in the nitroglycerin and gels it. The resulting cartridges have a density in the order of 1.55 to 1.59 g./cc., a detonation velocity in the order of 7800 meters per second, and are insensitive to. a No. 6 blasting cap and rie re.

A detailed description of preparing maximum density blasting gelatin with a freezing point depressant, such as formulation D above, is as follows: About 51 parts by weight of nitroglycerin and 41 parts by weight of nitroglycol are placed in a cooled Talley mixer where it is cooled down to approximately 5 C. About '7 parts by weight of nitrocellulose is added to the nitroglycerin together with about 1 part by weight of chalk and the mass thus formed is mixed, thereby evenly dispersing the nitrocellulose and antacid throughout the nitroglycerin-nitroglycol mass. The mixing is carried out with a minimum amount of agitation to prevent introduction of air bubbles. This is accomplished by rotating the mixing spirals of the Talley mixer slowly for about l to 3 minutes. The contents of the mixer are then poured into commercial cartridges, for example, 2 x 8 inch, 4 x 16 inch, or others. The lled commercial cartridges are then allowed to warm up to room temperature, whereby the nitrocellulose dissolves in the nitroglycerin and gels it. The gelation process can be speeded by storing the cartridge at 35-50 C. for several hours. The resulting cartridges have a density in the order of 1.53 to 1.58 g./cc., a ldetonation velocity in the order of 7800 meters per second, and are insensitive to a No. 6 blasting cap and rifle fire.

It is evident that there are numerous factors which will influence conditions for the most satisfactory operation of the invention, the actual limits of which cannot be established except by detailed study of each set of materials and the intermediate and finished products involved.

It is to be noted in accordance with the present invention that the speed of solution of the nitrocellulose and the gelation of the resulting mixture is of considerable importance. The temperature of mixing is, therefore, selected to `control this factor. y For example. the addition of materials like diglycerin tetranitrate slows down the rate of gelation becausethis compound forms a gel very slowly with nitrocellulose. On the other hand nitroglycol has the opposite effect so that the operation must be carried out at a low temperature when the nitroglycol is present.

It is seen, therefore, that this invention comprises mixing an explosive including nitroglycerin or nitroglycerin and a freezing point depressant and nitrocellulose at a temperature, which is low enough, so that thorough mixing of these ingredients is obtained without appreciable gelation, pouring the mixture into cartridges or other containers, such as, bombs and storing the cartridges or bombs at a temperature at which complete gelation will occur.

The blasting gelatins made in accordance with this invention are useful for commercial operations such as oil well shooting or in rock blasting Where an especially high brisance is desired. It will, of course, be necessary to use a stronger primer than normal. These blasting gelatins are also useful for military demolitions and in bombs where insensitiveness to rifle fire is desirable.

One advantage of the present invention comprises a process of preparing a blasting gelatin product of maximum density and brisance, which product may be simply poured into cartridges as contrasted to diflicult cartridging operations with rubbery mixes which heretofore have been employed in the art. A further advantage resides in the production of a gelatin having initially, a desirable high density which is maintained throughout storage, thereby making readily available a gelatin of suitable insensitiveness for military purposes.

What I claim and desire to protect by Letters Patent is:

1. A process for preparing maximum density blasting gelatin which comprises cooling a liquid explosive comprising nitroglycerin to a temperature from about C. to about 10 C. without freezing; adding a mixture comprising nitrocellulose and an antacid to said explosive; mixing the mass thus formed with a minimum amount of agitation, while maintaining said temperature; and discharging the cooled mixed mass and allowing said mass to warm and thereby gelatinize.

2. A process for preparing maximum density blasting gelatin which comprises cooling a liquid explosive comprising nitroglycerin and a soluble explosive organic compound, which is a freezing point depressant for the nitroglycerin, to a temperature from about -10 C. to about 10 C.; adding a mixture comprising nitrocellulose and an antacid to said explosive; mixing the mass thus formed with a minimum amount of agitation, while maintaining said temperature; and discharging the cooled mixed mass and allowing said mass to warm and thereby gelatinize.

3. A process for preparing maximum density blasting gelatin which comprises cooling a liquid explosive comprising nitroglycerin to a temperature from about 10 C. to about 10 C. without freezing; adding a mixture comprising nitrocellulose and an antacid to said explosive; mixing the mass thus formed with a minimum amount of agitation, while maintaining said temperature; and discharging the cooled mixed mass into containers and storing said containers at a temperature in the order of 35 to 50 C., thereby accelerating gelation.

4. A process for preparing maximum density blasting gelatin which comprises cooling a liquid explosive comprising nitroglycerin and a soluble explosive organic compound, which is a freezing point depressant for the nitroglycerin, to a temperature from about -10 C. to about 10 C.; adding a mixture comprising nitrocellulose and an antacid to said explosive; mixing the mass thus formed with a minimum amount of agitation, while maintaining said temperature; and discharging the cooled mixed mass into containers and storing said containers at a temperature in the order of 35 to 50 C., thereby accelerating gelation.

5. A process for preparing maximum density blasting gelatin which comprises cooling a liquid explosive comprising nitroglycerin and diglycerin tetranitrate to a temperature from about 0 to about 10 C.; adding a mixture comprising nitrocellulose and an antacid to said explosive; mixing the mass thus formed with a minimum amount of agitation, While maintaining said temperature; and discharging the cooled mixed mass and allowing said mass to warm and thereby gelatinize.

5. A process for preparing maximum density lasting gelatin which comprises cooling a liquid explosive comprising nitroglycerin and nitroglycol to a temperature from about 0 to about 10 C.; adding a mixture comprising nitrocellulose and an antacid to said explosive; mixing the mass thus formed with a minimum amount of agitation, while maintaining said temperature; and discharging the cooled mixed mass and allowing said mass to warm'and thereby gelatinize.

7. A process for preparing maximum density blasting gelatin which comprises cooling a liquid explosive comprising nitroglycerin, diglycerin tetranitrate and mononitro naphthalene to a temperature from about 0 to about 5 C.; adding a mixture comprising nitrocellulose and an antacid to said explosive; mixing the mass thus formed with a minimum amount of agitation, while maintaining said temperature; and discharging the cooled mixed mass and allowing said mass to warm and thereby gelatinize.

8. A process for preparing maximum density blasting gelatin which comprises cooling nitroglycerin to a temperature from about 0 to about 5 C. without freezing; adding a mixture of nitrocellulose and an antacid to said nitroglycerin; mixing the mass thus formed with a minimum amount of agitation, while maintaining said temperature; and discharging the cooled mixed mass and allowing said mass to Warm and thereby gelatinize.

HENRY W. BOTIS.

REFERENCES CETED The following references are of record in the file of this patent:

Naoum, Nitroglycerine and Nitroglycerine Explosives, page 298, Baltimore, 1928.

Certificate of Correction Patent No. 2,421,536. June 3, 1947. HENRY W. BOTTS It is hereby certified that error appears in the printed specication of the above numbered patent requiring correction es follows: Column 1, line 25, for 137 g./cc. read 1.37 g./cc.; and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of July, A. D. 1947.

LESLIE FRAZER,

First Assistant ommzsszoazer of Patents.

Certificate of Correction Patent No. 2,421,536. June 3, 1947.

HENRY W. BOTTS It is hereby certiied that error appears in the printed specification of the above numbered patent requiring correction as follows: Column 1, line 25, for 137 g./cc.

read 1.87 g./cc.; and that the sald Letters Patent should be read with this correction therein that the same may conform to the record of the ease in the Patent Office.

Signed and sealed this 15th day of July, A. D. 1947.

LESLIE FRAZER,

First Assistant Uommz'sszoner of Patents. 

